||Duffy S, Shackelton LA, Holmes EC. Rates of evolutionary change in viruses: patterns and determinants. Nat Rev Genet. 2008 Apr9(4):267-76 p.271 right column 2nd paragraphPubMed ID18319742
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||Primary source  abstract: "With the aim of elucidating evolutionary features of GB virus C/hepatitis G virus (GBV-C/HGV), molecular evolutionary analyses were conducted using the entire coding region of this virus."
||P.271 right column 2nd paragraph: "More controversial are those cases in which RNA viruses replicating with an RdRp [RNA-dependent RNA polymerase], rather than an RT [Reverse transcriptase], are reported to evolve slowly. Three types of viruses fall into this class — the rodent-associated hantaviruses and the flavivirus GB virus C (GBV-C), in which substitution rates in the range of 10^−7 subs/site/year have been inferred (primary sources), and some RNA viruses that infect plants (ref 47). Although the two animal viruses differ in genome structure, both are associated with chronic rather than acute infections, and the low evolutionary rates proposed for these viruses rest on the common assumption that they have co-diverged with their mammalian hosts over millions of years (primary source 46, refs 48, 49). However, given the small number of taxa that are involved in these co-divergence studies, especially for GBV-C, and that viruses can preferentially jump between related host species and those that live sympatrically (ref 50), studies utilizing serially sampled data (Box 3) are required to unequivocally show that these viruses evolve slowly."